Definition
The beginning of the portion of a runway that is usable for landing. It is the line across the runway where landing aircraft are expected to first touch down or pass over at a low height during the final phase of approach.
Plain English
The line at the start of the landing portion of the runway. It marks where the runway becomes available for touchdown.
Context Anchor
You see this term when judging the final part of an approach, choosing an aiming point, and making sure the airplane will cross the start of the landing area at a safe height.
Derivation
Threshold comes from Old English, originally meaning the piece of wood or stone at the bottom of a doorway — the line you cross when entering. The runway threshold is the same idea: the line you cross when entering the landing portion of the runway.
Why Pilots Care
Aiming short of or beyond the threshold can result in landing too early on unprepared surfaces or too far down the runway with insufficient stopping distance.
Intuition Check
Do not assume the runway approach threshold is always the physical end of the pavement. It is the start of the runway area available for landing in that direction, and it may be set in from the pavement end.
Example Sentence 1
On a normal approach, the pilot aims to cross the runway approach threshold about 50 feet above the ground.
Example Sentence 2
White threshold markings confirmed the beginning of the usable landing surface as the airplane crossed the fence on short final.